source: Memorial Sloan Kettering Cancer Center
Familial adenomatous polyposis (FAP) is a rare condition associated with less than 1 percent of colorectal cancers. It is characterized by polyposis, the development of thousands of polyps in the colon, often at a young age.
Most people with FAP that is left untreated eventually develop colorectal cancer, often around age 40. In rare cases, FAP can lead to the development of polyps or stomach cancer of the upper gastrointestinal tract.